1. Technical Field
The present invention relates to a system and method for drying industrial sludge using natural gas as the primary energy source. More specifically, the invention relates to a system and method using landfill gas as an energy source to dry industrial sludge, including that provided by landfill or wastewater processing, for fertilizer production, or to reduce the cost of waste disposal.
2. History of Related Art
Extracting natural gas from landfills is becoming more common throughout the United States due to new regulations set out by the EPA. While landfill gas has been used to generate electricity and in other industrial applications (e.g. boiler operation), it is typically not transported through the national gas pipeline system, due to the large amount of CO.sub.2 present (i.e., landfill gas is typically composed of 50% methane and 50% CO.sub.2). Therefore, most of the gas produced at landfills is flared to the atmosphere to destroy any harmful compounds (e.g., methane, which depletes the ozone layer, and various carcinogens, such as H.sub.2 S) that might be present, completely wasting the landfill gas energy potential.
Waste management professionals are constantly looking for ways to properly dispose of waste water and industrial sludge (sewage or landfill). Because of the limitations on, and cost of, landfill space, as well as the potential contamination liability brought about by the escape of liquids within the wet sludge to surrounding areas, the drying of such sludge is rapidly becoming a preferred disposal choice. Once the sludge is dried, it can be disposed at a much lower cost, or used as fertilizer to replenish minerals depleted by crop and landscape growth. However, one of the major expenses incurred by drying sludge is the cost of the energy used to generate the heat. Because landfill gas can be produced and sold for a fraction of the cost of pipeline natural gas, the present invention provides a system which combines the use of normally wasted landfill gas for use as an inexpensive energy source to dry sludge.
Therefore, the present invention provides a system which collects gas from a landfill and makes it available as an energy source to dry wet sludge, producing inexpensive fertilizer or dried waste for disposal, and operating to conserve natural gas resources.